The present disclosure relates to an electrophotographic type image forming apparatus.
An electrophotographic type image forming apparatus conventionally forms an electrostatic latent image on a surface of a photoreceptor and develops the electrostatic latent image in a toner image by a development device.
The photoreceptor is formed by providing a photosensitive layer having a thickness of 10 micrometers to several 10 micrometers on a surface of a cylindrical substrate. The photoreceptor is classified into one of an organic photoreceptor, a selenium and arsenic photoreceptor, an amorphous silicon photoreceptor (hereinafter, called as “an a-Si photoreceptor”) and so forth, depending on a main material forming the photosensitive layer. The organic photoreceptor is relatively inexpensive; however, frequent replacement is necessary because it is easily abraded. The selenium and arsenic photoreceptor has a longer life compared with the organic photoreceptor; however, it has a disadvantage of handling difficulty because it uses a toxic substance. On the other hand, although the a-Si photoreceptor is expensive more than the organic photoreceptor, it has an advantage of easily handling because it uses a nontoxic substance and is hard to be abraded to provide a long life (for example, five times or more of the life of the organic photoreceptor). However, because the a-Si photoreceptor is hard to be abraded, it is required to polish its surface by a polishing roller.
In the image forming apparatus using such a photoreceptor, a phenomenon called as “image flow” may occur depending on the use condition. The image flow is a phenomenon in which an image is blurred or a periphery of an image is spread. The image flow is caused because moisture in air is adsorbed on a surface of the photoreceptor and a surface resistance of the photoreceptor is lowered. On the surface of the photoreceptor, discharge product, such as nitrate ion and ammonium ion, generated by discharging of an electrical conductive member such as a charge roller is adhered. When the discharge product absorbs the moisture under a high humidity environment, the surface resistance of the photoreceptor is lowered. If the electrostatic latent image is formed under such a condition, the potential of the electrostatic latent image is leaked to its periphery to generate potential decreasing, and a boundary of the electrostatic latent image becomes unclear to cause the image flow.
The image flow occurs on the a-Si photoreceptor remarkably. This is because the surface of the a-Si photoreceptor is hard to be abraded even if a blade is pressed and the surface of the a-Si photoreceptor has a particle structure which easily absorbs the moisture. However, in the organic photoreceptor, if a dew condensation occurs on a surface of a member (for example, a charge roller and an intermediate transferring belt) with which the organic photoreceptor contacts and the surface of the member contains the moisture, the moisture is transferred to the surface of the organic photoreceptor to cause the image flow.
In order to eliminate the occurrence of the image flow, it is required to raise an apparatus inside temperature and to dry an apparatus inside. However, in recent years, it is difficult to raise the apparatus inside temperature because of improved technique for cooling the apparatus inside, and the image flow therefore easily occurs.
Then, in a conventional technique to eliminate the occurrence of the image flow, a supply amount of the toner to the photoreceptor from the development device is regulated depending on a rotation speed of the photoreceptor.